One reason that causes unequal throw in the ailerons is when the control horns are not mounted with the holes directly over the hinge area. Another is when the neutral position of the aileron does not correspond with a right angle between the control rod and the servo arm. It helps to first center the servo arm electrically with a live radio setup and then mount it on the servo for a right angle between the arm and the body.

If you have a computer radio, life is much easier and you can start to get lazy on your linkage setups knowing that you can program away any alignment or slop issues. Call me, "Mr. Lazy".